Hello all.
I have a 1999 Silverado 1500 4x4 wi the 5.3LS. I often (but not always) experience a hesitation after first starting it warm or cold. Starts up perfectly always, but once you get underway it’s like it’s starving for fuel. Once this passes (+- 15-20 seconds), truck runs perfect until I shut it down the next time. Dirty MAF, fuel pressure regulator or?? The puzzling part is once the hesitation clears it runs beautifully

 

Have you scanned for DTC codes? If not, do that first and report what they are.

Next, check your fuel pump pressure and then the operation of your fuel pressure regulator. Fuel pressure regulator can also be tested by hooking up a section of vacuum line to it and then sucking on it to see if it holds vacuum. If you unplug the vacuum line from the fuel pressure regulator and gas pours out, no need to test it as it's toast.